Sol-gel technology has been extensively studied for many years. Various sol-gel methods are typically used to fabricate metal oxides, especially silicon oxides and titanium oxides. The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Typical precursors are inorganic materials, such as metal alkoxides.
A common issue of sol-gel process derived inorganic material coatings is brittleness that causes cracking of sol-gel coatings. Inorganic-organic hybrid sol-gel systems have been proposed to address the issue. However, the proposed systems have not been adopted because of various difficulties in using these systems, e.g., premature gelation, incomplete curing, and the like. Yet, these hybrid inorganic-organic systems allow exploring new applications, such as antireflection coating for CR-39 based lens, medical technology, dental materials, and the like.
Hybrid sol-gel materials can be divided into two classes. The first class is based on organic molecules, prepolymers, or polymers embedded in an inorganic matrix. The second class is based on inorganic and organic components connected by covalent bonds. The presence of covalent bonds translates into various unique properties in the second class hybrid sol-gel materials. These covalent bonds can be formed by UV induced polymerization or as a product of the specific reaction. This disclosure relates primarily to the second class of hybrid sol-gel materials in which inorganic and organic components connected by covalent bonds.
Inorganic precursors of hybrid sol-gel compositions may include metal salts and metal alkoxides, such as set forth in the following formula:

The organic precursors can be an organic precursor or an inorganic-organic precursor as set forth in the following formulas, where R is an organic radical covalently bonded to Si:

The inorganic and organic precursors are typically combined and exposed to a catalyst to induce formation of the hybrid sol-gel.